In 2012, the coordinates of the named features in the Io portion of the International Astronomical Union Gazetteer of Planetary Nomenclature were updated from values from historical sources to values in the Voyager/Galileo SSI control network. The purpose of this work was to facilitate the identification of named features on Io. Dots representing the center coordinates of named features should fall in the centers of the features when displayed on any map product based on the Voyager/Galileo SSI reference frame. The extents and sizes of the named features were also updated; these data are approximate and are intended solely to give the user sufficient information to identify named features and their rough extents.
This new set of coordinates was derived using ArcMap version 10.0 and the 2011 Geologic Map of Io by David Williams et al. Vectors describing feature extents are based on the geologic contacts shown on this map. We are also grateful for help and advice provided by Dr. Rosaly Lopes and Dr. Jani Radebaugh.
The Io portion of the Gazetteer of Planetary Nomenclature web site now defaults to showing feature coordinates in the frame of the Voyager/Galileo SSI control network. The original coordinates (from unknown sources) are still retained in the gazetteer and can be viewed by selecting the desired coordinate set from a dropdown menu on the feature pages. The "Unknown" coordinates are now considered archival and will not be updated with new names or changes to approved names.